3 files changed, 31 insertions, 21 deletions

diff --git a/src/model/library.rs b/src/model/library.rs
index 518caca1..eee69675 100644
--- a/src/model/library.rs
+++ b/src/model/library.rs
@@ -2,15 +2,13 @@ use std::fmt::{self, Debug, Formatter};
 use std::hash::{Hash, Hasher};
 use std::num::NonZeroUsize;
 
-use comemo::Tracked;
 use once_cell::sync::OnceCell;
 
-use super::{Content, NodeId, Scope, StyleChain, StyleMap};
+use super::{Content, NodeId, Scope, StyleChain, StyleMap, Vt};
 use crate::diag::SourceResult;
 use crate::doc::Document;
 use crate::geom::{Abs, Dir};
 use crate::util::{hash128, EcoString};
-use crate::World;
 
 /// Definition of Typst's standard library.
 #[derive(Debug, Clone, Hash)]
@@ -27,11 +25,8 @@ pub struct Library {
 #[derive(Clone)]
 pub struct LangItems {
     /// The root layout function.
-    pub layout: fn(
-        world: Tracked<dyn World>,
-        content: &Content,
-        styles: StyleChain,
-    ) -> SourceResult<Document>,
+    pub layout:
+        fn(vt: &mut Vt, content: &Content, styles: StyleChain) -> SourceResult<Document>,
     /// Access the em size.
     pub em: fn(StyleChain) -> Abs,
     /// Access the text direction.
diff --git a/src/model/realize.rs b/src/model/realize.rs
index 9d7c4aec..46e0d678 100644
--- a/src/model/realize.rs
+++ b/src/model/realize.rs
@@ -1,8 +1,5 @@
-use comemo::Tracked;
-
-use super::{capability, Content, NodeId, Recipe, Selector, StyleChain};
+use super::{capability, Content, NodeId, Recipe, Selector, StyleChain, Vt};
 use crate::diag::SourceResult;
-use crate::World;
 
 /// Whether the target is affected by show rules in the given style chain.
 pub fn applicable(target: &Content, styles: StyleChain) -> bool {
@@ -22,7 +19,7 @@ pub fn applicable(target: &Content, styles: StyleChain) -> bool {
 
 /// Apply the show rules in the given style chain to a target.
 pub fn realize(
-    world: Tracked<dyn World>,
+    vt: &mut Vt,
     target: &Content,
     styles: StyleChain,
 ) -> SourceResult<Option<Content>> {
@@ -34,7 +31,7 @@ pub fn realize(
     for recipe in styles.recipes() {
         let guard = Guard::Nth(n);
         if recipe.applicable(target) && !target.is_guarded(guard) {
-            if let Some(content) = try_apply(world, &target, recipe, guard)? {
+            if let Some(content) = try_apply(vt, &target, recipe, guard)? {
                 realized = Some(content);
                 break;
             }
@@ -46,7 +43,7 @@ pub fn realize(
     if let Some(showable) = target.with::<dyn Show>() {
         let guard = Guard::Base(target.id());
         if realized.is_none() && !target.is_guarded(guard) {
-            realized = Some(showable.show(world, styles));
+            realized = Some(showable.show(vt, target, styles));
         }
     }
 
@@ -64,7 +61,7 @@ pub fn realize(
 
 /// Try to apply a recipe to the target.
 fn try_apply(
-    world: Tracked<dyn World>,
+    vt: &Vt,
     target: &Content,
     recipe: &Recipe,
     guard: Guard,
@@ -75,7 +72,7 @@ fn try_apply(
                 return Ok(None);
             }
 
-            recipe.apply(world, target.clone().guarded(guard)).map(Some)
+            recipe.apply(vt.world(), target.clone().guarded(guard)).map(Some)
         }
 
         Some(Selector::Label(label)) => {
@@ -83,7 +80,7 @@ fn try_apply(
                 return Ok(None);
             }
 
-            recipe.apply(world, target.clone().guarded(guard)).map(Some)
+            recipe.apply(vt.world(), target.clone().guarded(guard)).map(Some)
         }
 
         Some(Selector::Regex(regex)) => {
@@ -107,7 +104,7 @@ fn try_apply(
                 }
 
                 let piece = make(m.as_str().into()).guarded(guard);
-                let transformed = recipe.apply(world, piece)?;
+                let transformed = recipe.apply(vt.world(), piece)?;
                 result.push(transformed);
                 cursor = m.end();
             }
@@ -131,7 +128,7 @@ fn try_apply(
 #[capability]
 pub trait Show {
     /// Execute the base recipe for this node.
-    fn show(&self, world: Tracked<dyn World>, styles: StyleChain) -> Content;
+    fn show(&self, vt: &mut Vt, this: &Content, styles: StyleChain) -> Content;
 }
 
 /// Post-process a node after it was realized.
diff --git a/src/model/typeset.rs b/src/model/typeset.rs
index 451c6eb0..b422e4b6 100644
--- a/src/model/typeset.rs
+++ b/src/model/typeset.rs
@@ -10,5 +10,23 @@ use crate::World;
 pub fn typeset(world: Tracked<dyn World>, content: &Content) -> SourceResult<Document> {
     let library = world.library();
     let styles = StyleChain::new(&library.styles);
-    (library.items.layout)(world, content, styles)
+    let mut vt = Vt { world };
+    (library.items.layout)(&mut vt, content, styles)
+}
+
+/// A virtual typesetter.
+///
+/// Holds the state needed to [typeset] content. This is the equivalent to the
+/// [Vm](super::Vm) for typesetting.
+pub struct Vt<'a> {
+    /// The compilation environment.
+    #[doc(hidden)]
+    pub world: Tracked<'a, dyn World>,
+}
+
+impl<'a> Vt<'a> {
+    /// Access the underlying world.
+    pub fn world(&self) -> Tracked<'a, dyn World> {
+        self.world
+    }
 }